Constitutively active phosphatidylinositol-3 kinase (PI3K)/phosphatase and tensin homolog on chromosome 10 (PTEN) pathway signaling is common in EC and involved in the development and/or progression of the disease. PTEN deficiency and/or activating mutations/amplification in the PIK3CA gene that encodes the p110α catalytic subunit of PI3K have been frequently detected in EC patients. XL147 is a potent and highly selective inhibitor of the Class I PI3K family of lipid kinases. In addition, in vivo preclinical data have demonstrated that XL147 targets both proximal and distal signaling in the PI3K/PTEN pathway. Therefore, XL147 may have utility in the treatment of subjects with advanced or recurrent EC.